1. Technical Field
The present disclosure relates to organic electroluminescent devices, and, more particularly, to a top emitting organic electroluminescent device.
2. Description of Related Art
A typical top light emitting device comprises a bottom reflecting electrode and a top translucent electrode. Such a structure may result in enhanced emission at a specified wavelength and inhibited emission at non specified wavelength, causing a microcavity effect. The emitting light spectrum is sharpened and the color purity is improved due to the microcavity effect. For instance, with regard to emitting a single color light in a display with primary color pixels of RGB, the microcavity effect may enhance the emission and color purity, as well as increase the color gamut and color saturation.
However, microcavity has no beneficial effect for the use in lighting applications. Since the spectrum for lighting requires a full distribution of light intensity across visible light range (from 380 to 780 nm), microcavity effect only enhances emission at a certain wavelength, but inhibits emission at the other wavelengths, thereby adversely affecting the color spectrum of white light illumination.
Therefore, how to increase the light extraction efficiency and maintain its spectrum distribution of lighting devices have become urgent.